Some of the conventional wiper systems for vehicles such as automobiles can change the speed of the movement of the wiper depending on the intensity of rain fall. If the rain fall is substantial, the wiping speed is increased, and vice versa. Some wiper systems are provided with the intermittent operation mode in which the wiper system is activated in an intermittent manner. This mode is useful when there is minimal rain fall.
In an automobile equipped with such a wiper system, the speed of the wiper movement can be reduced in low speed range and increased in high speed range so that the optimum control of the wiper can be achieved in accordance with the vehicle speed.
When the vehicle is travelling at a high speed, the wind blows against the windshield at a high speed, and it is thus conceivable to reduce the wiping angle so that the force required for the movement of the wiper may be reduced, and, for instance, Japanese patent laid open publication (kokai) No. 02-136357 discloses such a wiping angle varying device. By thus allowing the wiping angle to be varied, it is possible to achieve an optimum wiping result at each vehicle speed.
However, according to such a conventional wiping angle varying device, the varying of the wiping angle may be required to take place during the wiping movement. Therefore, the motor which, for instance, consists of an electric motor is required to be powerful enough to change the wiping angle without being hindered by the force acting upon the wiper arm for the purpose of driving the wiper arm into the wiping movement by overcoming the frictional force which the wiper arm experiences. As a result, the wiper system tends to be bulky, and create problems in designing its mounting arrangement.